1. Field of the Invention
This invention relates generally to waste material treatment apparatus and processes, and more particularly to a self contained mobile apparatus and improved process for grinding, grating, macerating, chemically disinfecting, and drying medical waste materials on-site at health care related facilities.
2. Brief Description of the Prior Art
The following terms, as used herein, are recognized in government regulations, and in the trade, as distinguishing one type of medical waste treatment process from another. “STERILIZATION” is a process that destroys all microbial life including large numbers of bacterial endospores. “DISINFECTION” is a somewhat less lethal process than sterilization, which destroys or inactivates viruses, fungi, and bacteria (but not necessarily their endospores) on inanimate surfaces. “CHEMICAL DISINFECTION” is the use of a chemical agent to reduce significantly the numbers of active microorganisms (but not necessarily their endospores) from the surfaces of inanimate objects. “INCINERATION” is the process of burning waste in an incinerator. “AUTOCLAVING” is the process wherein waste material is sterilized with steam in an enclosed compartment. “UNRECOGNIZABLE” means that the original appearance of the waste item has been altered such that neither the waste nor its source can be identified. “GRINDING” is the physical process which pulverizes materials, thereby rendering them as unrecognizable, and for sharps, reduces the potential for the material to cause injuries such as puncture wounds. “SHREDDING” is the physical process which cuts, slices, or tears materials into small pieces. “CHLORINE DISINFECTION/MACERATION” is the process of shredding waste in the presence of a chlorine solution under negative pressure.
The description of infectious medical waste and the approved methods of handling this waste vary from state to state. Generally, infectious medical waste, or “red bag” waste is defined as including body fluids, microbiological waste, pathological waste, sharps, and animal waste. The term “red bag” is the red bag that hospitals are required by government regulations to use for containing infectious medical waste to clearly identify the contents. Red bag waste does not include radioactive materials, large quantities of chemicals, or large metal objects. A “log10 reduction” is a mathematically defined unit used in reference to level or degree of microbial inactivation. A 4 log10 reduction represents a 99.99% reduction in the numbers of active microorganisms, while a 6 log10 reduction represents a 99.9999% reduction in the numbers of active microorganisms. A process to meet the criteria set out in regulatory guidelines for “on-site” processing of infectious medical waste requires that it be disinfected to guarantee a 4 log10 reduction or 99.99%, and must yield a product residue which is unrecognizable as to the source.
It is important to point out the basic microbiology and chemistry as it relates to “sterilization” and “disinfection”. As discussed above, “sterilization” destroys all microbial life including large numbers of bacterial endospores. On the other hand, “disinfectants”, if properly used, will eliminate all pathogenic vegetative organisms but not all endospores. Since most endospore fortners are non-pathogenic, an effective disinfectant will kill the broad range of potential pathogens. Hypochlorites (calcium and sodium) are relatively inexpensive, fast acting, and have a broad spectrum of anti-microbial activity. Their use as disinfectants is limited by their corrosiveness, inactivation by organic matter, and relative instability. The microbiocidal activity of chlorine is largely attributed to hypochlorous acid (HOCl). Hypochlorite ion (OCl) posses about 1/80th the germicidal capacity of hypochlorous acid (HOCl). The chemical reaction which causes disassociation of hypochlorous acid (HOCl) to the less microbiocidal form hypochlorite ion (OCl), C12, and various sodium salts is dependent on pH. As the pH increases, more hypochlorite ion (OCl) is formed and the microbiocidal activity decreases. As the pH decreases, the concentration of hypochlorous acid (HOCl) increases and the microbiocidal activity increases. Hypochlorous acid (HOCl) is the “microbiocidal” component of the disassociated end products of sodium hypochlorite (NaOCl). The production of hypochlorous acid (HOCl) and resultant microbiocidal activity is at its greatest when the pH is in the range of from 4 to 6.
At a pH of 1.0 to 4.5, the reaction is driven to 90% to 95% C12. At a pH range of 4.5 to 6.0, the reaction is driven to 90% to 95% hypochlorous acid (HOCl). At a pH range greater than 6.0, the reaction is driven to 80% to 95% hypochlorite ion (OCl) and is less microbiocidal. If a sodium hypochlorite (NaOCl) disinfectant is adjusted to a pH of 4.0 to 6.0, the microbiocidal properties are enhanced to a factor of more than 100 times.
The present invention utilizes a sodium hypochlorite (NaOCl) solution adjusted to a pH of from about 4.0 to 6.0 to increase the hypochlorous acid (HOCl) component and significantly increase the microbiocidal activity of the disinfectant.
Traditionally, the majority of infectious medical waste has either been “incinerated” or “autoclaved” to render the end product non-infectious and unrecognizable. The residue of incineration has been deposited in landfills as fly ash or bottom ash. Incineration has become an unacceptable method due to recent air quality standards and problem areas concerning air emissions during incineration such as carcinogenic organic, dioxins, and furans, as well as acid gases. The controversy over incineration has resulted in substantial public opposition to the construction of new incinerators and frequent demonstrations demanding closure of existing incinerators.
“Autoclaving”, wherein the bulk waste material is sterilized with steam in an enclosed compartment, also has many objectionable characteristics. Autoclaving alone does not change the physical appearance of the waste, resulting in uncertainty and fear among subsequent handlers. In many cases, autoclaved materials have been rejected at landfills. The cost of construction and operation precludes autoclaving as an acceptable alternative for treating large volumes of infectious medical waste. Other methods such as chemical disinfection, microwaving, thermal or dry heat inactivation, chlorine disinfection/maceration, and moist heat disinfection have been proposed. Most of these other methods either cannot meet the total volume requirements and/or do not significantly reduce the microbial colony count to acceptable levels.
Another major problem with prior art treatment methods is that the process is usually carried in large treatment plants which are built or fixed at a location remote from the waste generating facility, because of their requirements for large amounts of power, fluids, heat, and potential of fluid residue hazards.
Thus, another important objection to incineration, autoclaving, and other traditional methods of infectious waste treatment and disposal is the logistics of transporting the infectious medical waste material from the waste generating facility to the incinerator, autoclaving facility, microwaving facility, or chemical treatment plant over public thoroughfares and highways.
Federal regulations are very strict if infectious medical waste is taken away from the premises of the hospital or health care facility (“off-site”) for incineration or other methods of disposal. The U.S. Department of Transportation has an entire set of regulations including special handling, recording, packaging, and storage, which must be followed by the health care facility, the hauler, and the receiver of the infectious waste. The health care facility must also have liability insurance, in the event of an accident before the waste materials are destroyed. However, if the waste materials are processed on the health care facility premises (“on-site”), there are substantially fewer requirements on the health care facility. Thus, the health care facility is faced with either transporting the infectious waste to a remote treatment plant or with a massive capital expenditure to build an on-site waste treatment system.
There are several patents which disclose various waste treatment apparatus and sterilization and disinfection processes, most of which require a large system of apparatus fixed-in-place on-site (not mobile) and require placement in close vicinity to sources of supply of power, fluids, and heat, or placement at a remote site which requires providing these sources of supply at the remote location. Thus, most of these systems require the health care facility to install the system on-site or to transport the waste to a remote location.
Swisher, Jr. et al, U.S. Pat. No. 6,446,887 discloses a portable medical waste plant for loading, reducing, and sterilizing medical waste. The system includes a frame supporting a generally sealed containment chamber, a lift assembly having a lifter mounted on a track assembly, a hopper mounted on the frame near the lift and in communication with a material feeder, a first grinder in communication with the material feeder, a first conveyor positioned to receive medical waste from the first grinder, and a second grinder in communication with the first conveyor. The system further includes a second conveyor positioned to receive waste from the second grinder, and an autoclave in the containment chamber in communication with the second conveyor assembly for thermally disinfecting the waste. The autoclave includes a plurality of steam inlets, a waste inlet opening, and a waste outlet opening for discharging waste to a third conveyor assembly. The third conveyor assembly is positioned to receive waste from the autoclave and to convey the waste to a disposal container. The system further includes a steam generation plant mounted on the frame in the containment chamber and in communication with the steam inlets of the autoclave.
Devine et al, U.S. Pat. No. 5,720,438, commonly owned with the present application, discloses a mobile self-contained apparatus and process for grinding, grating, macerating, chemically disinfecting, and drying infectious waste material on-site. A trailer contains a hopper, a first and second grinder/grater, four enclosed conveyors, drying and filter apparatus, and sources of power, chemical disinfectant, and fresh water. Bagged infectious waste material in a cart is lifted and dumped into a hopper, fed to a first grinder/grater, ground and grated into particles, immersed in a sodium hypochlorite (hypochlorous acid) chemical disinfectant solution, and conveyed by an enclosed upwardly inclined screw conveyor to a second grinder/grater. The particles are sprayed one or more times with the disinfectant and thoroughly mixed together as they are conveyed in the inclined conveyor and are dumped from the inclined conveyor into the second grinder/grater and further ground, grated, and macerated into smaller particles, and air dried to produce a dry confetti-like material which is unrecognizable as to the source. The confetti-like material is conveyed by an enclosed horizontal screw conveyor to an enclosed vertical screw conveyor where it is passed upwardly to an enclosed rotatable discharge screw conveyor which discharges the confetti-like material into a receptacle. The enclosed system operates under negative pressure produced by a suction fan which draws the air within the system through a HEPA filter to remove chemical fumes, airborne dust, odors and bacteria.
Devine et al, U.S. Pat. No. 5,720,438 is commonly owned with the present invention, and is hereby incorporated herein by reference. The present invention is an improvement over Devine et al, U.S. Pat. No. 5,720,438, in that the present invention not require a second grinder/grater, a second generator, or a horizontal conveyor between the inclined conveyor and the vertical conveyor. The modified grinder/grater of the present system also incorporates a slotted grid plate and cutter blade arrangement that effectively shreds and disintegrates the plastic material of the “red bag” that contains infectious medical waste and overcomes the problem of sticking and gumming caused by the bag material. The present system also incorporates a different disinfectant spraying arrangement that more efficiently disinfected the particles of waste. Thus, the present system is housed in a much small trailer chassis, is less expensive to manufacture and operate, and the process of treating infectious waste material is accomplished more efficiently, in fewer steps and in less time.
Kline et al, U.S. Pat. No. 5,656,248 discloses a multi-stage treatment system for infectious waste includes a shredding stage, a granulating stage, a wetting stage, a disinfecting stage, and a dewatering stage which define a continuous treatment flowpath for the infectious waste. A plurality of blades shred the waste in the shredding stage, then the waste is injected with volatile disinfectant chemicals which are mixed immediately before injection. A plurality of blades in a granulating stage then fragment the waste to a smaller particle size. The granulating stage insures that the waste is granulated to a sufficiently small size to facilitate the use of a relatively low concentration of a highly reactive disinfectant. Chemicals are mixed to form a volatile, highly reactive disinfectant which is then immediately injected into the waste downstream of the shredding stage. A plurality of jets wet the waste mixture in the wetting stage with the heated aqueous disinfectant. A flow restriction removes excess aqueous liquid from the disinfected waste in the dewatering stage and renders the product suitable for landfilling. A control system controls the temperature of the disinfectant to maintain an optimum temperature for a desired kill rate.
Kaneko, U.S. Pat. No. 5,397,535 discloses a process for converting various kinds of used and potentially infectious medical articles such as injection needles into an aggregate for construction materials such as concrete. The articles are first crushed into pieces to such an extent that the shape of the articles cannot be visually identified. Subsequently, the crushed medical articles and particulate absorbent are introduced into a mixer and mixed and heated therein to a temperature above 180° C. by use of a heater in combination with frictional heat generated as the mixer blade is rotated, whereby the crushed infectious medical waste articles are completely sterilized. The particulate absorbent serves to absorb any unpleasant odor or toxic gas which is generated from the crushed infectious medical articles during heating.
Miller et al, U.S. Pat. No. 5,346,142 discloses a fixed-in-place apparatus and method for shredding and sterilizing medical waste material wherein the waste material is initially shredded by a primary shredder, sprayed with a sterilant and mixed in a screw conveyor, fed into a second higher speed shredder for further shredding, fed into a second screw conveyor for further mixing, fed into a turbo blender which further mixes and shatters any substantially sized particles remaining after shredding and moves it into a conveyor, and it is finally discharged as unrecognizable waste material. The disclosure is silent as to the type of sterilant used.
Goldner et al, U.S. Pat. No. 5,270,000 discloses an apparatus and process for treating medical hazardous wastes to process them into waste similar to domestic refuse which can be removed or disposed of like normal domestic refuse or can be supplied for recycling after sorting. The infectious refuse is passed through a microwave chamber fitted with a plurality of microwave sources disposed next to each other and subjected to disinfection therein. The apparatus has a two-stage construction of microwave chamber and temperature maintenance chamber. The microwave chamber has a dense microwave field distribution for heating the refuse to or above a selectable minimum temperature. The temperature maintenance chamber connected to the outlet of the microwave chamber holds the refuse at least the minimum temperature during a minimum residence time.
Noetzel, U.S. Pat. No. 5,213,774 discloses a mobile disinfection apparatus for hospital waste that has a worm conveyor leading from the bottom of the charging shaft at the back of a trailer bed to the mouth of a rotary tube reactor or rotary kiln enclosed in a heated hood which can be subdivided into separately heated zones. The reactor is formed with scoops which lift the waste comminuted in the charging shaft and cause it to cascade to contact the sterilizing medium and the sterilized waste passes into a discharge housing in which the waste is separated from the sterilizing medium which is recycled. The waste can be discharged and compacted by a worm conveyor which can be swung laterally outwardly from its transport position to discharge the waste for further handling like household or municipal waste.
Pearson, U.S. Pat. Nos. 5,173,257 and 5,116,574 disclose a fixed-in-place chemical disinfection process and apparatus for the treatment of infectious medical waste utilizing ozone wherein the medical waste is subjected to an ozone liquid or gas disinfectant, shredded, fed to a separation tank, fed to from 1 to 6 reactor vessels where ozone gas bubbles pass through the infectious waste material. The ozone disinfection process requires contacting times of from about 5 to about 45 minutes to effectively disinfect the waste.
Pearson, U.S. Pat. Nos. 5,077,007 and 5,078,965 disclose a fixed-in-place chemical disinfection process and apparatus for the treatment of infectious medical waste utilizing ozone wherein the medical waste is subjected to an ozone liquid or gas disinfectant, shredded, fed to a separation tank, fed to a fluidized bed reactor vessel where ozone gas bubbles pass through the infectious waste material. The ozone disinfection process requires contacting times of from about 5 to about 45 minutes to effectively disinfect the waste.
Mennel et al, U.S. Pat. No. 5,054,696 discloses a fixed-in-place medical waste disposal system for disposing of biologically contaminated waste situated inside a rigid, form-stable container which includes a screw auger which shreds the material and may mix the shredded mass with a liquid disinfectant solution. The auger transports the mass to a hammermill which disintegrates the shredded mass into an unrecognizable particulate. The disclosure is silent as to the type of disinfectant fluid used.
Pearson, U.S. Pat. No. 4,884,756 discloses a fixed-in-place infectious waste treatment system wherein the waste is placed into a feeding channel and moved by a ram into a series of shredders and is then gravity fed into a disinfecting fluid contained within an enclosed decontamination and separation device. The disclosure is silent as to the type of disinfectant fluid used or whether the material is discharged in a soaked condition.
Wilson et al, U.S. Pat. No. 4,618,103 discloses a relatively small hospital waste disposal system wherein a hammermill, a disinfectant solution, and separator tank divided into collecting pools which are adapted for connection to a sewer for disposing of the disinfectant are contained in a sealed cabinet which is placed in patient wards of a hospital. The disclosure is silent as to the type of disinfectant solution used.
Wilson et al, U.S. Pat. No. 4,578,185 discloses a fixed-in-place hospital waste disposal system wherein an inclined belt conveyor transfers waste materials through slitted curtains and drops it into a shredder while it is sprayed with a sodium hypochlorite solution having a pH of 8.5 and then enters a hammermill. The particles are then fed through a particle separator where solid particles are separated from the liquid disinfectant for independent evacuation. The liquids are evacuated to the sewer system and the solids are deposited in a cart. The system also includes vacuum ventilation elements to maintain any released bacteria or particles in the system until completely processed. As pointed out above, when the pH range of sodium hypochlorite is greater than 6.0, the reaction is driven to 80% to 95% hypochlorite ion (OCl) and is less microbiocidal than a solution with a pH of 6.0 or less.
Lovercheck, U.S. Pat. No. 3,547,577 discloses a wheeled vehicle for processing and sterilizing refuse such as trash and domestic garbage which carries a shredding machine that shreds the garbage which is then heated by a heater, a compactor which compresses the shredded material into briquettes, and a tank wherein the briquettes are contacted with a microbiocidal gas such as ethyelene oxide, propylene oxide, methyl bromide, or betapropiolactone.
The present invention overcomes the problems discussed above and provides a very cost effective alternative to transporting infectious waste and building new on-site waste treatment systems for each health care facility.
The present invention is distinguished over the prior art in general, and these patents in particular by a mobile self-contained apparatus and process for grinding, grating, macerating, chemically disinfecting, and drying infectious waste material on-site. A trailer contains a hopper, a grinder/grater, enclosed conveyors, drying and filter apparatus, and sources of power, chemical disinfectant, and fresh water. Bagged infectious waste material in a cart is lifted and dumped into a hopper, sprayed with a sodium hypochlorite (hypochlorous acid) chemical disinfectant solution, fed to a grinder/grater, ground, grated, and macerated into small particles, sprayed again and immersed in the chemical disinfectant solution, and conveyed by an enclosed upwardly inclined screw conveyor where they are thoroughly mixed together, and dried to produce a dry confetti-like material which is unrecognizable as to the source. The confetti-like material is discharged into an enclosed vertical screw conveyor where it is passed upwardly to an enclosed rotatable discharge screw conveyor that discharges the confetti-like material into a receptacle. The enclosed system operates under negative pressure produced by a suction fan that draws the air within the system through a HEPA filter to remove chemical fumes, airborne dust, odors and bacteria.